Attenuation of UHF signals regarding the sensitivity verification for UHF PD measurements on power transformers

The reliability of electrical energy networks depends on the quality and availability of electrical equipment like power transformers. Local failures inside their insulation may lead to catastrophic breakdowns and might cause high outage and penalty costs. To prevent these destroying events power transformers are e.g. tested on partial discharge (PD) activity before commissioning and currently also during service. The current work deals with the electromagnetic PD detection method, also known as the UHF-Method. The disadvantage of the UHF-Method is still the missing possibility for a calibration or at least a verification of the sensitivity. The so-called Sensitivity Check might show in future a relation between unconventionally measured UHF quantities to the PD apparent charge level in pC. An import aspect is the attenuation of UHF signals within power transformers which is investigated in this paper.